addons list empty by default?

Very proud after building a HTPC from parts ordered individually from web shops!

XBMC installed like a dream from the XBMCbuntu CD.

Now I'm trying to customise the setup by getting some add ons for getting TV, radio, etc.
The problem is I'm not sure that the internet is working properly.
When I go to system - settings - addons, I can't get a list of avaiable addons, and searches come up empty.

Also, In the videos menu I cannot find youtube which should be there? Or does that need to be installed first?

So I suspect it is something to do with internet access. But the thing is, If I log out, and in again as the same user in XBMCbuntu instead of XBMC, internet is working fine (I'm typing this in Chromium on XBMCbuntu).

Is there a way to check in XBMC that I have internet access? And a way to get access to the internet setup?

Many thanks!